[SauronOfMordor]

I can't imagine nuclear power driving a space ship and especially a manned one. The mass of fat-nucleus atoms needed to shield it would render it literally impossible.

Distance is also a shield.

Once you get to Low Earth Orbit via conventional means, you can hook up to a nuke power section via tether (we can make long and very strong strings these days) and have it pull you to Mars orbit via high-efficiency ion drive

[The Red Zone]

The world's longest extension cord, huh. Someone oughtta do the math for how heavy it would need to be in order to carry the requisite current... shoot, even to support itself against high atmospheric winds.